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New Delhi (CNN)It’s the bold image of India most often seen in ad campaigns, films and music videos.

But what is Holi and why do Indians celebrate it?

Hindu devotees play with color during Holi celebrations at the Banke Bihari temple on March 27, 2013 in Vrindavan, India.

The beginning of Spring

Holi is a Hindu festival that marks the start of Spring.

Celebrated across India, it’s an ancient festival with the first mentions of it dating all the way back to a 4th century poem.

It was even described in detail in a 7th century Sanskrit play called "Ratnavali," written by the Indian emperor Harsha.

"Witness the beauty of the great cupid festival which excites curiosity as the townsfolk are dancing at the touch of brownish water thrown … Everything is colored yellowish red and rendered dusty by the heaps of scented powder blown all over," wrote Harsh.

Indian students smear colored powder during an event to celebrate the Hindu festival of Holi in Kolkata on February 26, 2018.

How it looks today

Although a Hindu festival, Holi is celebrated by Indians across the country and is a great equalizer.

Children can douse elders with water, women splash men with color and the rules of caste and creed are briefly forgotten with everyone taking part.

The evenings are spent visiting friends and family.

A national holiday, it takes place on the last full moon day of the Hindu lunisolar calendar month, which is usually March.

This year’s national holiday falls on Friday, March 2.

The festival takes place a day earlier in the eastern states of West Bengal and Odisha. In some parts of northern Uttar Pradesh state, the festivities take place over a week.

An Indian artist dressed as Hindu god Lord Shiva takes part in a procession ahead of the Holi festival in Amritsar on February 26, 2018.

Mythological roots

The roots of the festival lie in the Hindu legend of Holika, a female demon, and the sister of the demon, King Hiranyakashayap.

Hiranyakashayap believed he was the ruler of the universe and superior to all the gods.

But his son, Prahlad, followed the god Vishnu, the preserver and protector of the universe.

Prahlad’s decision to turn his back on his father left Hiranyakashayap with no choice. He hatched a plot with Holika to kill him.

It was a seemingly foolproof plan; Holika would take Prahlad onto her lap and straight into a bonfire. Holika would survive because she had an enchanted shawl that would protect her from the flames.

But the plan failed. Prahlad was saved by Vishnu and it was Holika who died as she was only immune to fire if she was alone. Soon after, Vishnu killed Hiranyakashayap and Prahlad became king.

The moral of the story is that good always triumphs over evil.

Indian Hindu devotees throw colored powder during celebration of Holi Festival at Sriji temple in Barsana in the northern Indian state of Uttar Pradesh on February 23, 2018.

The love story behind Holi

In modern day Holi celebrations, Holika’s cremation is often reenacted by lighting bonfires on the night before Holi, known as Holika Dahan.

Some Hindus collect the ashes and smear them on their bodies as an act of purification

Rangwali Holi takes place the next day and is an all-day affair where people throw and smear colored powder on each other.

Indian college girls throw colored powder to one another during Holi festival celebrations in Bhopal on February 28, 2018.

The tradition of throwing colored powder and water is believed to originate from the mythological love story of Radha and Krishna.

Krishna, the Hindu god depicted with dark blue skin, is believed to have complained to his mother about Radha’s fair complexion.

To ease her son’s sadness, his mother suggests he Radha’s skin color by smearing her with paint. It’s believed that this is where the custom of smearing loved ones with color during Holi came from.